Inorganic carbon outwelling from mangroves and saltmarshes drives coastal acidification

Concentrations of alkalinity (TA) and dissolved inorganic carbon (DIC) in porewater as well as in surface water measured during timeseries (fixed location) and spatial surveys (fixed time period) were compiled from 38 mangrove- and 8 saltmarsh-dominated creeks and estuaries. We used data from creeks that were predominantly surrounded by mangrove or saltmarsh vegetation and with minimal confounding factors such as mixed vegetation or large catchments. These creeks were located in either pristine or anthropologically impacted estuaries or coastal areas. Anthropologically impacted areas were defined as areas that were affected by nearby urban or agricultural activities, potentially delivering pollutants, e.g., sewage or fertilizers, to creeks. We also included pristine mangrove- and saltmarsh dominated estuaries. When available, environmental parameters were also recorded, i.e., season, salinity, temperature, pH, dissolved oxygen (DO), water level, porewater tracer radon (222Rn), partial pressure of carbon dioxide (pCO2), dissolved organic carbon (DOC), particulate organic carbon (POC), nitrate and nitrite (NOx), ammonium (NH4), total nitrogen (TN), phosphate (PO4), and total phosphorus (TP). Methods used to determine parameters are explained in each corresponding reference.